<?php
/**
 * @package   AdminTools
 * @copyright Copyright (c)2010-2014 Nicholas K. Dionysopoulos
 * @license   GNU General Public License version 3, or later
 */

defined('_JEXEC') or die;

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


include_once("fixedbytenotation.php");


class GoogleAuthenticator
{
	static $PASS_CODE_LENGTH = 6;
	static $PIN_MODULO;
	static $SECRET_LENGTH = 10;

	public function __construct()
	{
		self::$PIN_MODULO = pow(10, self::$PASS_CODE_LENGTH);
	}

	public function checkCode($secret, $code)
	{
		$time = floor(time() / 30);
		for ($i = -1; $i <= 1; $i++)
		{

			if ($this->getCode($secret, $time + $i) == $code)
			{
				return true;
			}
		}

		return false;
	}

	public function getCode($secret, $time = null)
	{

		if (!$time)
		{
			$time = floor(time() / 30);
		}
		$base32 = new FixedBitNotation(5, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567', true, true);
		$secret = $base32->decode($secret);

		$time = pack("N", $time);
		$time = str_pad($time, 8, chr(0), STR_PAD_LEFT);

		$hash = hash_hmac('sha1', $time, $secret, true);
		$offset = ord(substr($hash, -1));
		$offset = $offset & 0xF;

		$truncatedHash = self::hashToInt($hash, $offset) & 0x7FFFFFFF;
		$pinValue = str_pad($truncatedHash % self::$PIN_MODULO, 6, "0", STR_PAD_LEFT);;

		return $pinValue;
	}

	protected function hashToInt($bytes, $start)
	{
		$input = substr($bytes, $start, strlen($bytes) - $start);
		$val2 = unpack("N", substr($input, 0, 4));

		return $val2[1];
	}

	public function getUrl($user, $hostname, $secret)
	{
		$url = sprintf("otpauth://totp/%s@%s?secret=%s", $user, $hostname, $secret);
		$encoder = "https://chart.googleapis.com/chart?chs=200x200&chld=Q|2&cht=qr&chl=";
		$encoderURL = $encoder . urlencode($url);

		return $encoderURL;
	}

	public function generateSecret()
	{
		$secret = "";
		for ($i = 1; $i <= self::$SECRET_LENGTH; $i++)
		{
			$c = rand(0, 255);
			$secret .= pack("c", $c);
		}
		$base32 = new FixedBitNotation(5, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567', true, true);

		return $base32->encode($secret);
	}
}

